Kontact - KOrganizer Alternatives for iPhone

Google Calendar is a robust, cloud-based scheduling and time management platform developed by Google. It allows users to create and manage events, set up reminders, share calendars with others, and sync seamlessly across devices, making it an essential tool for personal, academic, and professional organization.

Apple Calendar is a personal calendar application developed by Apple Inc., designed to seamlessly integrate with your Apple ecosystem whether you are on macOS or iOS. It allows you to manage your schedule, appointments, and events efficiently, synchronizing across all your devices.

Org-mode is a powerful and flexible mode for GNU Emacs, designed for note-taking, project planning, to-do list management, and authoring documents. It utilizes simple plain text files with intuitive markup.